There has recently been a marked increase in the use, particularly among young people, of some forms of smokeless tobacco (chewing tobacco and snuff) in the United States. There is also increasing epidemiologic and clinical evidence of local and systemic pathologic effects associated with this habit yet there are few experimental studies. Smokeless tobacco is customarily placed on the surface of the oral mucosa, and rarely ingested, so that its effects must be mediated almost entirely via the oral mucosal lining. This research proposal considers the relationship between permeability and the penetration of certain components of smokeless tobacco across the oral mucosa as well as the direct effects on the mucosa. Specifically, the project will examine (a) the chemical nature of the permeability barrier in keratinized and nonkeratinized oral regions, (b) the contribution of salivary mucin to permeability barrier function, (c) the penetration of the tobacco associated components, nicotine and the carcinogen, nitrosonornicotine (NNN) across these different regions (d) the effect of interactions between these components and of ethanol on the penetration of NNN across oral mucosa, and (e) the morphologic effects of nicotine on oral mucosa. The permeability barrier in different regions of porcine oral mucosa will be examined by quantifying the relative amounts of lipids, glycolipids and glycoproteins in specific histologic strata of the epithelia using thin layer chromatography and SDS-polyacrylamide gel electrophoresis. Penetration of the tobacco components, NNN and nicotine, will be determined by determining permeability constants for the same mucosal regions using radiolabelled compounds. Morphologic and pathologic effects will be examined in porcine tissue in vitro and in rats in vivo, using light and electron microscopy. These studies represent a comprehensive investigation of the relationship between oral mucosal barrier function and the penetration and effects of components of tobacco on the tissues. The work also has health implications extending well beyond smokeless tobacco, for there are other substances, such as alcohol and the nitrosamines present in many foodstuffs, that may be capable of initiating oral disease if they penetrate the oral lining.